1. Field of Invention
The present invention relates to transportable systems having both direct and projection viewing modes of operation, and to electro-optical backlighting panels for use therein.
2. Brief Descriptiopn of the State of the Art
Presently, most portable computing systems include a flat liquid crystal display (LCD) panel for directly viewing video imagery displayed thereon. Portable computer systems of this type include notebook, laptop, and palmtop computers.
In general, prior art LCD display panels have essentially the same basic construction in that each includes a conventional backlighting structure affixed to the rear surface of either a passive or active matrix LCD panel. Several different backlighting panel designs are described in the technical paper xe2x80x9cNew Backlighting Technologies for LCDsxe2x80x9d by Kevin J. Hathaway, et al., published at pages 751-754 in SID 91 Digest. In recent times, the xe2x80x9clight pipexe2x80x9d backlight design, in particular, has been widely used in many commercially available notebook computers.
Specifically, prior art xe2x80x9clight pipexe2x80x9d backlight assemblies are constructed from a rectangularly shaped light guiding panel, typically fabricated from an acrylic plastic sheet having a thickness of about 4 millimeters or so. Along the opposite side edges of the acrylic sheet, a pair of miniature fluorescent light tubes are mounted within suitably designed light reflective mounts. The function of the fluorescent light tubes is to produce and direct incoherent light into the interior of the light guiding panel within which the light is typically bounded by the well known principle of xe2x80x9ctotal internal reflectionxe2x80x9d. Under ideal conditions, light will not leak out of the surfaces of the acrylic plastic sheet. However, light can be extracted or leaked out from these surfaces by forming therein scratches, undulations, or any other means of locally altering the critical angle for total internal reflection. By achieving light extraction in this manner, the backlighting panel can be used to illuminate an LCD panel.
In order to compensate for the decrease in light intensity in the light guiding panel at distances away from the fluorescent tubes, a light extracting pattern is permanently formed on one or both surfaces of the light guiding panel. Typically the light extracting pattern is realized as a dot pattern permanently embossed or sand-blasted upon the front surface of the acrylic light guiding panel. The density of the dot pattern is made to increase quadratically with distance from the fluorescent light tubes in order to achieve light intensity compensation along the light guiding panel. With this construction, a constant backlighting brightness is maintained across the light guiding panel.
In order to integrate (i.e. diffuse) the spotted distribution of light emanating from the light extracting pattern towards the LCD panel, a first light diffusing structure is placed on top of the light guiding panel. Typically, the first light diffusing structure is made from one or more thin sheets of translucent plastic attached to the front surface of the light guiding panel. In most commercial xe2x80x9clight pipexe2x80x9d backlight designs, a second light diffusing structure is placed over the rear surface of the light guiding panel to diffuse the spotted distribution of light emanating from the permanently formed light extracting pattern towards the reflective surface disposed behind the light guiding panel. Typically, the second light diffusing structure is made from one or more thin sheets of translucent plastic attached to the rear surface of the light guiding panel. Together, the light guiding panel, fluorescent light tubes, light diffusing sheets and the light reflective layer cooperate to produce a plane of backlight having a uniform spatial intensity for optical processing by the LCD panel affixed to the backlighting panel.
While the prior art backlighting panel design described above has proven useful in the direct viewing of visual imagery on LCD display screens, its permanently formed light extracting pattern renders it unsuitable in projection viewing modes of operation. This fact is best illustrated by example.
In the recently introduced notebook computer, marketed under the tradename xe2x80x9cCruiser(trademark)xe2x80x9d by EMCO/REVERED Technologies, Inc. and generally described in U.S. Pat. No. 5,353,075 to Conner, et al., the above-described xe2x80x9clight pipexe2x80x9d backlighting panel design is used to construct a portable computer system having both direct and projection viewing modes of operation. In the direct viewing mode, the prior art backlighting panel is positioned against the active-matrix LCD panel. Each time the user desires to operate the notebook computer in its projection viewing mode, the user must mechanically reconfigure the Cruiser(trademark) notebook computer by physically removing the prior art backlighting panel in order to reveal the active matrix LCD panel, and provide an optically clear path for the light rays to pass therethrough.
Recently, Intellimedia, Corporation of Benton Harbor, Michigan has introduced the IntelliMedia(trademark) Multimedia Presentation System which consists of portable computer system having a flat LCD projection panel which can support both direct and projection viewing modes. In the direct viewing mode, the user of this system is required to affix an auxiliary backlighting panel beneath the LCD panel. Then, when operated in the projection viewing mode, the user is required to remove the auxiliary backlighting panel, and place the LCD panel upon an external overhead projector, much like that required by the Cruiser(trademark) computer system.
While the above-described image display systems provide both direct and projection viewing modes, they both nevertheless suffer from a number of serious shortcomings and drawbacks which make them less than commercially attractive products.
In particular, the need to physically remove the entire backlighting panel from the Cruiser(trademark) computer during its projection viewing mode, poses a substantial risk of damage to the backlighting panel and imposes an added responsibility upon the user to safely store the same when the computer system is operated in its projection viewing mode. Also, from a practical standpoint, the need to place the display panel assembly of the Cruiser(trademark) computer and the entire display panel of the Intellimedia(trademark) system upon an overhead projector during projection viewing, necessitates that the user either tote an overhead projector along with such prior art systems, or have access to one during projection viewing. Consequently, such prior art image display systems lack the versatility of operation in either direct or projection modes of viewing, and thus are incapable of functioning as truly portable systems.
Thus, there is a great need in the art for an improved image display system which has direct and projection viewing modes, without the shortcomings and drawbacks of the prior art systems.
Accordingly, a primary object of the present invention is to provide a novel electro-optical light panel construction particularly designed for use in image display systems having both direct and projection viewing modes of operation.
A further object of the present invention is to provide a portable image display system having direct and projection viewing modes.
A further object of the present invention is to provide an image display system in the form of a portable computer-based system which can be easily configured into its projection viewing mode using an electro-optical light panel having light scattering and non-scattering states of operation selectable under electronic control.
A further object of the present invention is to provide a portable device for illuminating the electro-optical display panel of a computer-based image display system having direct and projection viewing modes, in order to project focused video images therefrom onto a desired viewing surface.
A further object of the present invention is to provide a portable computer-based image display system with a rear housing panel that is hingedly connected to a light guiding panel and supports a light reflective surface and covers the rear light transmission aperture when the system is operated in its direct viewing mode.
A further object of the present invention is to provide such a portable computer-based image display system, in which the display panel assembly thereof includes a thin light focusing panel, such a Fresnel or holographic lens panel, for use during the projection viewing mode.
A further object of the present invention is to provide such a portable computer-based image display system, in which a film slide or optical transparency carrying imagery can be placed upon the display surface of the display panel assembly thereof and the imagery viewed in either the direct or projection viewing mode.
A further object of the present invention is to provide a flat electro-optical display panel assembly having direct and projection viewing modes of operation, and an electro-optical light panel having a light emission state in which light is emitted from the electro-optical panel during the direct viewing mode of operation, and a light transmission state in which externally generated light is permitted to pass through the electro-optical panel without substantial scattering during the projection viewing mode of operation.
A further object of the present is to provide such a flat display panel assembly as described above, in which the light emission and transmission states of the electro-optical light panel are electronically selectable during the first and second modes of operation, respectively.
A further object of the present invention is to provide a flat display panel as described above, in which the electro-optical light panel is realized as a polymer dispersed liquid crystal (PDLC) panel assembly having a light-diffusive state of operation that is electronically selectable during the direct viewing mode, and also a light non-diffusive state of operation that is electronically selectable during the projection viewing mode of operation, without removal or other physical modification of the light panel.
A further object of the present invention is to provide a flat display panel construction different from the display panel described above, in which the electro-optical light panel is realized as a electroluminescent (EO) panel assembly having a layer of electroluminescent material that emits light from the panel during the direct viewing mode, and permits externally generated light to pass through the electro-luminescent panel during the projection viewing mode without substantial scattering.
A further object of the present invention is to provide a novel computer-based image display system which incorporates such a display panel assembly construction, and can be easily reconfigured for its projection viewing mode of operation without physical modification to the display panel assembly construction.
A further object of the present invention is to provide such a portable computer-based image display system with a housing having a light aperture that permits an external source of intense light to pass directly through the display panel assembly in order to project focused video images therefrom onto a desired viewing surface.
A further object of the present invention is to provide such a portable computer-based image display system with a hinged housing panel disposed behind the display panel assembly for supporting a light reflective panel and covering the light aperture when the system is operated in its direct viewing mode.
A further object of the present invention is to provide such a portable computer-based image display system, in which a film slide or optical transparency carrying imagery can be placed upon the display surface of the display panel assembly of the present invention and the imagery viewed in either the direct or projection viewing mode.
A further object of the present invention is to provide a portable computer-based image display system having both direct and projection viewing modes of operation, in which xe2x80x9cspatially-multiplexedxe2x80x9d images of 3-D objects or imagery are viewable through an LCD display panel during the direct viewing mode, and viewable on a wall surface or projection screen during the projection viewing mode, so as to permit the 3-D object to be perceived with stereoscopic depth sensation when the spatially-multiplexed images are viewed through polarized viewing spectacles.
A further object of the present invention is to provide a portable image display system having both direct and projection viewing modes of operation so that it is capable of selectively displaying color video images on its display surface during its direct viewing mode, and projecting such video images onto a projection display surface during its projection viewing mode.
A further object of the present invention is to provide a portable pen-computing device capable of supporting pen-based data entry operations and stereoscopic image display in both direct and projection viewing modes of operation.
A further object of the present invention is to provide a portable light projection accessory device that is particularly adapted for use with the portable computer-based systems of the present invention.
A further object of the present invention is to provide such a portable light projection device having first and second housing portions that are interconnected by a foldable structure that permits these housing portions to be selectively reconfigured for use during the projection viewing mode of operation, and for compact storage during the direct viewing mode of operation.
A further object of the present invention is to provide such a portable light projection device, wherein the first housing portion contains an intense light source and a light polarizing filter for producing an intense source of polarized light, and an optics assembly for projecting the produced polarized light, and wherein the second housing portion contains an image projection lens that can be adjustably positioned with respect to the display panel assembly thereof for projecting a focused video image onto a desired viewing surface.
A further object of the present invention is to provide a method of projecting images from such a portable computer-based system, by moving the rear housing panel away from the display panel assembly, positioning an external projection lens in front of the display panel assembly, electrically selecting the projection viewing mode of operation for the display assembly, and projecting an intense source of polarized light through the display panel assembly so that when the intense polarized light rays pass through the display panel assembly and are optically processed thereby and focused by the projection lens, a focused video image is projected onto a desired viewing surface.
An even further object of the present invention is to provide such a computer-based image display system in the form of either a palmtop, laptop or notebook computer, personal digital assistant or personal communicator which, with the portable light projecting device hereof, can be easily stored and transported in a lightweight carrying case having physical dimensions on the same order as the portable computer itself.
These and other objects of the present invention will become apparent hereinafter and in the claims to Invention.